A bomb planted on a motorcycle exploded near the office of India's main opposition party in the southern city of Bengaluru wounding 16 people, including eight policemen, police said.
Al Jazeera's Sohail Rahman, reporting from the Indian city of Mumbai, said on Wednesday that a second blast occurred about three hours later on the main road to the airport. No early reports of casualties from the second attack have been reported.
Lalrokhuma Pachau, the director general of police in the Karnataka state, of which Bengaluru is the capital, said the motorcycle was parked about 100 meters from the office of the Bharatiya Janata Party in Bengaluru's Malleshwaram neighbourhood.
Police cordoned off the area and forensic experts were gathering evidence from the blast site.
The injured were being treated at nearby hospitals, where doctors said the condition of two people was serious, Pachau said.
Scores of party supporters were in the building at the time of the explosion, with elections to the Karnataka provincial assembly due to be held early next month.
Witnesses said the blast was so powerful that nearby buildings shook and window panes were shattered. Pachau said it was too early to say what kind of explosive had been used or who was responsible for the blast.
Three cars and several scooters were charred in the blaze that followed the blast. A police bus parked nearby was also badly damaged.
Malleshwaram is a residential area in the heart of Bengaluru (formerly known as Bangalore), India's information technology hub.
Throngs of people crowded around the explosion site and police had to push them back to allow sniffer dogs and bomb experts to gather evidence.